Revert "[heap-profiler] Do not treat WeakMap values as weak."

This reverts commit c34042cc.

Reason for revert: Wrong table type was used

Original change's description:
> [heap-profiler] Do not treat WeakMap values as weak.
> 
> For the WeakHashTable objects only mark keys as weak while leaving values as strong references.
> 
> BUG=chomium:773722
> 
> Change-Id: Iabd5ba293d05fe68a2af6503fcdd711ecc182482
> Reviewed-on: https://chromium-review.googlesource.com/730771
> Commit-Queue: Alexei Filippov <alph@chromium.org>
> Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#48985}

TBR=ulan@chromium.org,alph@chromium.org,mlippautz@chromium.org

Change-Id: Ia2ddef5b2422d4cbb8c4710e24ed0885a9a5b284
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: chomium:773722
Reviewed-on: https://chromium-review.googlesource.com/740721Reviewed-by: Alexei Filippov <alph@chromium.org>
Commit-Queue: Alexei Filippov <alph@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48986}

src/objects/hash-table.h

@@ -597,15 +597,17 @@ class WeakHashTable : public HashTable<WeakHashTable, WeakHashTableShape<2>> {
                                                    Handle<HeapObject> key,
                                                    Handle<HeapObject> value);
 
-  // Returns the index to the value of an entry.
-  static inline int EntryToValueIndex(int entry) {
-    return EntryToIndex(entry) + 1;
-  }
+  static Handle<FixedArray> GetValues(Handle<WeakHashTable> table);
 
  private:
   friend class MarkCompactCollector;
 
   void AddEntry(int entry, Handle<WeakCell> key, Handle<HeapObject> value);
+
+  // Returns the index to the value of an entry.
+  static inline int EntryToValueIndex(int entry) {
+    return EntryToIndex(entry) + 1;
+  }
 };
 
 // This is similar to the OrderedHashTable, except for the memory

src/profiler/heap-snapshot-generator.cc

@@ -1345,21 +1345,12 @@ void V8HeapExplorer::ExtractFixedArrayReferences(int entry, FixedArray* array) {
     return;
   }
   switch (it->second) {
-    case JS_WEAK_COLLECTION_SUB_TYPE: {
-      WeakHashTable* table = WeakHashTable::cast(array);
-      for (int i = 0, capacity = table->Capacity(); i < capacity; ++i) {
-        int key_index =
-            WeakHashTable::EntryToIndex(i) + WeakHashTable::kEntryKeyIndex;
-        int value_index = WeakHashTable::EntryToValueIndex(i);
-        SetWeakReference(table, entry, key_index, table->get(key_index),
-                         table->OffsetOfElementAt(key_index));
-        SetInternalReference(table, entry, value_index, table->get(value_index),
-                             table->OffsetOfElementAt(value_index));
-        // TODO(alph): Add a strong link (shortcut?) from key to value per
-        //             WeakMap the key was added to. See crbug.com/778739
+    case JS_WEAK_COLLECTION_SUB_TYPE:
+      for (int i = 0, l = array->length(); i < l; ++i) {
+        SetWeakReference(array, entry, i, array->get(i),
+                         array->OffsetOfElementAt(i));
       }
       break;
-    }
 
     // TODO(alph): Add special processing for other types of FixedArrays.
 

test/cctest/test-heap-profiler.cc

@@ -558,7 +558,7 @@ TEST(HeapSnapshotWeakCollection) {
       ++weak_entries;
     }
   }
-  CHECK_EQ(1, weak_entries);  // Key is the only weak.
+  CHECK_EQ(2, weak_entries);
   const v8::HeapGraphNode* wm_s =
       GetProperty(env->GetIsolate(), wm, v8::HeapGraphEdge::kProperty, "str");
   CHECK(wm_s);